The invention deals with the problem of different types of sound recording tape cassettes being available which are not compatible. In the field of dictating machines alone four different types of cassettes have become common lately. They are:
1. the so-called Grundig cassette according to German Industrial Standard DIN 32 750 T, PA0 2. the mini-cassette according to DIN 32 750 W, PA0 3. the micro-cassette, and PA0 4. the mini-M-cassette.
These cassettes differ in many respects. Their dimensions are different as well as their reel cores, the spacing between cores, and the centering means, and finally also the provision of "scanning windows" for sound, playback, and erasing heads. As a result of these differences the various cassettes can be used only in tape recorders designed specifically for their employment. Once a user has decided to adopt a certain system, he will be bound to continue to make use of it unless he is willing to replace the whole system, putting up with the economic loss involved.
In greater firms or clerical offices different systems are bound to clash, and then dictating and playback sets must be available for each system. That is uneconomical. DE-OS No. 32 34 584 discloses a cassette tape recorder which includes two winding shafts arranged at variable spacing for adaptation to different cassettes. The winding shafts are guided by arcuate slots formed in a plate which receives the cassettes and are displaced along the path defined by these slots. Before any change of the type of cassette the proper spacing must be adjusted between the winding shafts, a cumbersome affair for unskilled users. If they forget to make the adjustment, the cassettes or the tape recorder may become damaged.